The invention relates to means for electrically connecting the shadow mask to an internal conductive layer of a cathode ray tube. A cathode ray tube typically comprises an envelope having a neck containing an electrode system for generating three electron beams, and a substantially rectangular display window, the inside surface of which carries a display screen with phosphor elements luminescing in different colours. The display screen is coated with an electrically conductive layer. A substantially rectangular shadow mask comprising a large number of apertures, is positioned adjacent the display window, and directs each electron beam to luminescent phosphor elements of one colour. The shadow mask is attached to a substantially rectangular supporting frame. The supporting frame is suspended in the display window from pins connected to an upright edge portion of the display window, each of which has at least partly the shape of a truncated cone. The shadow mask is electrically connected to the conductive layer by at least one contact spring, a part of which engages one of the pins and another part of which engages the layer.
Such a cathode ray tube is known from German Offenlegungsschrift 26 22 695. The electric connection between the shadow mask and the electrically conductive layer in this case is produced by at least one contact spring which is interposed between a mask suspension means and a pin having the shape of a truncated cone, and which is fixed on the pin by the suspension means.
The pressure which the contact spring exerts on the electrically conductive layer depends upon the distance between the place where the contact spring engages the suspension means and the point of electrical contact with the conductive layer. If a good electric connection is to be produced for various types of cathode ray tubes having tolerances in the dimensions of the shadow mask and/or the display window, contact springs of different types or with varying tolerances are necessary. Moreover, since the contact spring engages the suspension means in a resilient manner, the contact spring can perform different movements with respect to the display window for example, vibrations present in the shadow mask transmitted to the suspension means, can result in the contact spring rubbing the electrically conductive layer so that the electric connection is detrimentally influenced.